Clinical and Cognitive

All AIBL study participants complete a comprehensive range of tests performed by trained staff. These typically take between one and two hours. The neuropsychological battery tests were selected on the basis that together they covered the main domains of cognition that are affected by Alzheimer’s Disease and other dementias. These tests were chosen so that results from our participants were comparable with those from other similar large studies, and all are internationally recognised as having good evidence of their reliability and validity.

All participants complete a detailed questionnaire regarding family medical history (including family history of psychiatric disorders, dementia, and other neurological illnesses), personal medical history, medication use and smoking, and questions about current and past alcohol and illicit drug use.

Lifestyle Research Stream Highlights

Demonstration that the presence of amyloid in the brains of apparently healthy older individuals was strongly related to cognitive decline over an 18-month period. In a series of papers, this important work has helped better to understand the interaction between brain amyloid levels and cognition in apparently healthy older adults and those with Mild Cognitive Impairment . (Lim et al., 2012. Neurology, 79(16), 1645-1652)

Demonstration that one measure from a typical psychometric memory test is strongly predictive in picking healthy elderly at risk for developing Mild Cognitive Impairment (MCI), and MCI cases at risk of developing Alzheimer’s disease. Moreover, combining the memory score with a measure of amyloid load using PiB PET almost doubles the predictive value in healthy elderly.

Subjective memory complaints are still highly regarded by some researchers as a good indicator of the step before objective cognitive decline. However, the AIBL team has shown that memory complaints, as conceptualised based on a single question, are not a strong predictor of cognitive status or decline, but are related to mood factors in this cohort. Continuing studies examining the detailed and specific nature of memory complaints will help to inform research and clinical practice.

Ongoing work suggests that high-functioning elderly people with PiB PET evidence of significant amyloid deposition have the same rate of cognitive decline as the average person, but that decline may be masked on cognitive testing. This important finding has ramifications for interpretation of cognitive findings and highlights the importance of collecting data on education levels and premorbid IQ levels.

Continual cognitive/clinical assessment and categorisation of the AIBL cohort is the foundation for all research conducted within AIBL. This comprehensive undertaking has involved David Ames personally reviewing all AIBL participant files over 5 different timepoints, and these files are subsequently reviewed for cognitive data accuracy by the neuropsychology team at MHRI. It is this attention to detail by a leading clinician in the field of AD research that has resulted in the high diagnostic accuracy within AIBL, and sets it from many other large-scale cohort studies.

Identified particular genotypes influencing the rate of cognitive decline and development of AD in β-amyloid positive individuals. That is, we have shown that the rate of cognitive decline associated with amyloid burden can change from two to ten years depending on the genotype associated with two gene loci.

Data from the AIBL study has provided the foundation for the development of international clinical trials of drugs designed to forestall amyloid related cognitive deterioration in otherwise healthy older adults.